The present invention relates to implantable neural stimulators, and more particularly to a way of increasing the distance from which an external remote control device is able to control and monitor the operation of a fully implantable neural system, such as a fully implantable cochlear implant system.
Representative cochlear implant systems are disclosed in the following U.S. patents, each of which is incorporated herein by reference: U.S. Pat. Nos. 5,824,022; 5,584,869; 5,603,726; and 6,219,580. A representative fully implantable cochlear implant system is disclosed in U.S. Pat. No. 6,308,101, also incorporated herein by reference.
A fully implantable cochlear implant system, or other fully implantable neural system, requires the use of a bi-directional telecommunications link, e.g., a radio frequency (RF) link, to communicate between the implant components and a remote control device for the purpose of setting the operating parameters of the implant system, and for monitoring its operation. The operating parameters of the implant system may include adjusting sensitivity, volume, program selection, ON/OFF control, and the like.
In a fully implanted cochlear implant system, such as that described in U.S. Pat. No. 6,308,101, the functions of the implant system are split between electronic circuitry contained in two separate housings: (1) an implantable speech processor (ISP) and (2) an implantable cochlear stimulator (ICS). The two housings are coupled to each other through a compact multi-turn coil through mutual inductance, as taught, e.g., in U.S. patent application Ser. No. 10/346,482, filed Jan. 17, 2003, now issued as U.S. Pat. No. 7,054,691 on May 30, 2006, which application and patent are assigned to the same assignee as the present application, and which application and patent are incorporated herein by reference. In such a system, the implantable speech processor (ISP) receives and transmits control signals through the multi-turn coil, using mutual inductance, by way of an imperceptible amount of energy which couples into the radiating modes. This link is therefore very limited in its transmission and reception range, which is typically only about 10–20 inches.
In the past, it has been necessary to hold the remote control device very close to an implantable device, .e.g., on or very near the skin surface above the location where the implant device is implanted. This is cumbersome and unsightly. In use, with the remote control device held on the skin above the implant location, it is usually difficult for the user to see the controls or displays on the remote control device when it must be held adjacent to the implant location.
In order to allow the remote control device to communicate with a fully implantable device from a farther distance, it has been necessary to increase the energy level of the signal transmitted to the implant device. Disadvantageously, such increase in transmitted signal strength only works in one direction, and increases the power consumption of the remote control device.
While radio repeater systems have been in use for many years for telephone, television and all forms of communications that use conventional rf communication links over large distances through the atmosphere or space, they have not, to applicant's knowledge, been adapted for use with medical implant systems where the signal must traverse through body tissue and fluids.
Therefore, it is evident that a need exists for improvements in the manner in which a remote control device communicates with a medical implant system, i.e., in the way that a remote control device communicates bi-directionally with a fully implanted device.